Difficult shifting 6-speed fixed
Tech Contributor
Joined: Aug 2008
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From: Oak Hill Virginia
OK ... I just got off the phone with Tremec Tech Dept (talked to Rob). Tired of non-concurring info on this.
Tremec Tech Dept said:
1) ALL GM vehicles with at T-56 transmission started using the carbon blocker rings in the 2002 model year. He said GM had to approve the design, and therefore the 2002 model year is when the carbon rings made it into production for ALL GM vehicles. So, the info in the link I references saying F-body T-56s started using carbon blocker rings in 1998 is false.
2) He said that Tremec has tested various synthetic transmission oils for compatibility with the T-56. He said that Mobil 1 Full Synthetic AFT IS recommend even for the T-56 transmissions with the paper blocker rings. They DO NOT recommend Royal Purple or Redlline because of additives that they use that are not in Mobil 1. He didn't give me a whole list of non-approved fluids, only the RP and RL ... there could be others. But bottom line is Tremec says Mobil 1 ATF has been tested to be comparable with the paper blockers.
This is info directly from the Tremec Tech Dept ... don't shoot the messenger.
PS - cdkcorvette7, looks like there's still a slight discrepancy on if the carbon rings started with 2001 or 2002 model year Vettes ... but I was just told that ALL GM vehicles with T-56 transmissions started using the carbon rings in the 2002 model year.
Tremec Tech Dept said:
1) ALL GM vehicles with at T-56 transmission started using the carbon blocker rings in the 2002 model year. He said GM had to approve the design, and therefore the 2002 model year is when the carbon rings made it into production for ALL GM vehicles. So, the info in the link I references saying F-body T-56s started using carbon blocker rings in 1998 is false.
2) He said that Tremec has tested various synthetic transmission oils for compatibility with the T-56. He said that Mobil 1 Full Synthetic AFT IS recommend even for the T-56 transmissions with the paper blocker rings. They DO NOT recommend Royal Purple or Redlline because of additives that they use that are not in Mobil 1. He didn't give me a whole list of non-approved fluids, only the RP and RL ... there could be others. But bottom line is Tremec says Mobil 1 ATF has been tested to be comparable with the paper blockers.
This is info directly from the Tremec Tech Dept ... don't shoot the messenger.
PS - cdkcorvette7, looks like there's still a slight discrepancy on if the carbon rings started with 2001 or 2002 model year Vettes ... but I was just told that ALL GM vehicles with T-56 transmissions started using the carbon rings in the 2002 model year.
looks like we're never going to get an answer that all the "experts" agree on. When I called tremec they told me it was 01+... I know for a fact my 01 has carbon rings in it because it was just torn down and rebuilt by a forum vendor a few weeks ago and I watched it.
Le Mans Master
Joined: Mar 2002
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From: PNW
looks like we're never going to get an answer that all the "experts" agree on. When I called tremec they told me it was 01+... I know for a fact my 01 has carbon rings in it because it was just torn down and rebuilt by a forum vendor a few weeks ago and I watched it.
Who knows ... maybe some late built model year 2001 Vettes got carbon blockers - what's the month/year built info on the door sticker?
In any case, Tremec Tech said you can use Mobil 1 full synthetic ATF in any of them, regardless if they have paper or carbon blockers. I asked if Tremec actually did extensive testing with Mobil 1 synthetic ATF on T-56s with paper blockers for compatibility, and he said "yes".
Last edited by ZeeOSix; Nov 17, 2011 at 04:03 PM.
Tech Contributor
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From: Van Buren Arkansas
Wounded Warrior Escort '11
Well, I know all too well what Mobil1 did to my BW transmission. No offense meant to Mobil1 as its a good product. Tremec transmissions are probably a bit different than the BW transmissions in whatever ways.
Tech Contributor
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From: Oak Hill Virginia
Race Director
Joined: Aug 2003
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From: Lake Mary Florida
Think I'll look into this for my '01 which has 68K now. I have changed the differential fluid but haven't done the trans fluid. This may just improve it some. Thanks for the reminder.
BTW shifting not so much the issue for me and its very helpful to change your clutch fluid regularly, but I'm looking to see if the fluid change will smooth out the transmission some.
BTW shifting not so much the issue for me and its very helpful to change your clutch fluid regularly, but I'm looking to see if the fluid change will smooth out the transmission some.
Last edited by Jet-Jock; Nov 19, 2011 at 02:28 PM.
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From: Lake Mary Florida
Tech Contributor
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From: Oak Hill Virginia
Eric is a GM engineer. I didn't know until recently either.
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I put RP in my '99 manual, when it had 60k on the clock. It now has 120k or so, and no real problems. The shifting improved alot with an MGW install, and it never really has gotten worse. It is hard to get into gear sometimes, but it isn't really a problem.
Drifting
Joined: Apr 2010
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From: Central FL
Unless it's just my imagination shifting doesn't seem to be as "smooth" now then when I got my car 5 months ago especially into 1st. I really baby my car too. The previous owner installed a short throw shifter and several other mods so who knows of he ever changed the fluid and with what. If the fluid is new does mobil 1 smooth shifts out as opposed to regular ATF?
Race Director
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From: Lake Mary Florida
Unless it's just my imagination shifting doesn't seem to be as "smooth" now then when I got my car 5 months ago especially into 1st. I really baby my car too. The previous owner installed a short throw shifter and several other mods so who knows of he ever changed the fluid and with what. If the fluid is new does mobil 1 smooth shifts out as opposed to regular ATF?
Melting Slicks
Joined: Jun 1999
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From: NJ
Use GM Manual Trans Fluid.
Originally GM published a tech sheet saying Dexron VI was back compatible for all Dexron III requirements, but then came out with an addendum that it's not to be used in manual transmissions.
Melting Slicks
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I had my Z06 out this weekend and noticed it was shifting a little rough...confirmed the fluid is a bit dirty, so I'll be changing mine out...going with Mobil-1!!
Tech Contributor
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From: Oak Hill Virginia
Didn't know that... You don't happen to have a link to the addendum do you?
Melting Slicks
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From: NJ
Drifting
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I know this has been beat to death, but the resident expert in my book is Bill Curlee, and just like the old EF Hutton commercials say, when Bill speaks, people listen and Bill says that he likes Amsoil and that it will not harm the paper in the older transmissions. Just more fuel for discussion! 
Zuti
Zuti
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Just changed mine yesterday and put Dexron VI in it!
Melting Slicks
Joined: Jun 1999
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From: NJ
Did the same thing. I switched it out as soon as I found out. Fortunately mine is a 2004, so I guess it wouldn't have made a difference anyway. If it's any consolation, I checked with a high-volume Corvette Chevy dealer tech, & he uses DexVI in all C5's.....told me he never even heard of the addendum!